MOTION
81
PROBLEMS.
1. Find the path and the velocity of a particle which moves so that
its position at any instant is given by the following pairs of equations:
(a) x = at, y = bt.
(b) x = at, y = at — | gt2.
(c) x -at, y ~ b cos coi.
(d) x = a sin otf, y = R
(e) a; = a sin co£; ?/ = a cos oit.
(f) a; = a sin at, y = 6 sin co£. / \ _ £^ _ _1.
\o/ *^ ^^ 7 y — ^^
2. Prove the relation v = V-x2 + y'2 + z2.
81. Radial and Transverse Components of Velocity. — The magnitude of the velocity along the radius vector is, according to the results of the preceding section,
dr
-j7 dt
(D
The expression for the velocity at right angles to r is obtained by considering the motion of the projection of the particle along a perpendicular y to r. When the particle moves through cfe, its projection moves through r dd, Fig. 50, therefore the required velocity
is
rdd '' dt
,r£-rt.
dt
(2)
FIG. 50.
The components vr and vp may be expressed in terms of x and y by differentiating the equations of transformation
r2=x2+2/2 (3)
and
(4)